The present invention generally relates to the surface mounting of integrated circuit (IC) devices to a printed circuit (PC) board, and more particularly to test sockets for the test and burn-in of IC devices. The invention is particuarly suited to the testing of leadless IC chips, but is not limited to such applications.
The increased capabilities of IC chips have led to increased input/output (I/O) densities and alternative techniques for mounting IC chips to printed circuit (PC) boards involving leadless IC chips. For example, ball grid array (BGA) mounting techniques have been developed to replace pin grid array (PGA) mounting approaches in order to achieve more densely packed contacts and smaller contact dimensions (in the order of 25 mils.). To facilitate the testing and burn-in of leadless IC devices, special test sockets have been devised to hold these devices and to temporarily connect them to a PC test board. Test sockets for leadless IC devices most commonly employ stamped or formed metal contact pins for achieving electrical interconnection between the I/O contacts of the IC device being tested and the PC test board circuits. Such socket designs have a relatively high profile and relatively high capacitance and inductance making them undesirable for high speed applications. They also require soldering of the socket pins to the PC board and do not operate efficiently with IC devices having noncompliant I/O contacts. Sockets having elastomeric contactors which do not require soldering have also been devised. These test sockets utilize flexible wire filaments which extend in a perpendicular relation to the contact points. Such wire filaments are generally not reliable and will not hold up with repetitive use. In addition, they are not likely to withstand the thermal shock while testing an IC device.
Still another known IC test socket design is a test socket having high profile, spring-loaded pins, called "pogo pins." Heretofore, the use of pogo pins in test sockets have been limited to relatively long, single-ended pogo pins wherein one end of each pogo pin is a fixed end soldered to the PC board and the other end is spring-loaded. Again, the relatively high profile of such test sockets make them unsuitable for high speed test applications. Also, since the fixed ends of the pogo pins are soldered to the PC board, such sockets are relatively difficult to remove.
The present invention overcomes the disadvantages of conventional test sockets for leadless IC devices by providing a low profile test socket suitable for high frequency test applications which will provide efficient and solderless contacts for both the PC board and the IC devices being tested.